Nucleic Acids in Human Glioma Treatment: Innovative Approaches and Recent Results

Figure 2

Scheme of mi/si RNA processing pathway. MiRNAs are first transcribed into long primary miRNAs (pri-miRNAs) by polymerase II or, in few rare cases, by polymerase III. Primary miRNAs are cleaved in the nucleus by an RNAse III enzyme, Drosha, inducing the conversion into precursor miRNAs (pre-miRNAs). Pre-miRNAs are transported into the cytoplasm by exportin-5 and subsequently processed by Dicer, a cytoplasmic endonuclease RNAse III enzyme, that generates a miRNA duplex. The functional strand of the mature miRNA is then incorporated into the RISC (RNA-induced silencing complex), that mediates the degradation or the translation inhibition of the target mRNA. For siRNA-mediated RNAi, double-stranded RNAs (dsRNAs) are chemically synthesized and then introduced into cell. dsRNAs are directly cleaved into small double-stranded siRNAs by Dicer and then incorporated into the RISC leading to target mRNA degradation.